Monday, September 6, 2010

Farmers interested in alternative energy technologies for the farm can learn more about the small-scale biodigester developed by Ohio State University ecological engineers. The technology will be demonstrated at Farm Science Review, Sept. 21-23 at the Molly Caren Agricultural Center in London, Ohio.

Jay Martin, a researcher with the Ohio Agricultural Research and Development Center, has developed a modified fixed-dome digester that can make methane from manure, which can either be burned as an alternative to natural gas or propane, or converted to electricity using a generator. The 300-gallon biodigester, installed at Waterman Agriculture and Natural Resources Laboratory in Columbus, is designed specifically to cater to average-sized and smaller livestock farms – around 150 dairy cows on average.

"There are less than 200 digesters working on livestock farms in the United States, and those digesters are designed for large-scale industrial dairy operations in the range of 10,000 or 15,000 head. And they are expensive – around $1 million to implement," said Martin, who is also an associate professor with the Department of Food, Agricultural, and Biological Engineering. "Right now, only farms with around 1,000 cows or larger can use digesters. You crunch the numbers and more than 95 percent of the livestock farmers in the U.S. can't use this technology to create renewable energy."

Recognizing the need for smaller-scale, affordable biodigesters, Martin and his colleagues turned to technologies widely implemented in China, India and South American nations like Costa Rica, and adapted a biodigester for Ohio's climate.

The result is a biodigester that can generate 500 liters of biogas a day -- 60 percent methane and 40 percent carbon dioxide. For now, 10 gallons of manure is added per day, and the renewable energy generated is enough to cook a few meals.

The biodigester technology being demonstrated at Farm Science Review is a mini version (about 5 gallons) of the Waterman model. The mini biodigester can create enough biogas to roast a few marshmallows.

Martin said that the technology being demonstrated is the first step in determining how successful biodigesters can be on Ohio dairy farms.

"One of the challenges of a biodigester is the air temperature. The microbes that turn the organic matter into biogas are sensitive to colder temperatures," said Martin. "How the biodigester performs in winter will aid in determining if such technology can be successful in Ohio."

The Waterman biodigester was installed last October and researchers, including graduate students Richard Ciotola and Juan Castano, began monitoring biogas generation this spring. If successful, Martin envisions scaling up the biodigester to 5,000 or 10,000 gallons.

"A thousand-gallon biodigester is probably the minimum right now that a farmer would need to get up and running, and the smaller-scale is much more affordable – about $100 per cow for the system," said Martin. "The key to the design is based on optimum amount of manure that can be collected per day for the greatest amount of biogas produced."

Researchers are still exploring minimum and maximum manure loads that the 300-gallon biodigester can handle. Too little manure, and not enough biogas is created. Too much manure, and the pH drops, killing off the microbes that create the biogas.

Martin envisions farmers using biodigester technology in such applications as heating water for cleaning milk parlors. In addition, through the conversion process of manure to biogas, the displaced liquid – rich in inorganic nitrogen and phosphorus – can be applied to field crops as fertilizer.

The mini biodigester model will be on display at Farm Science Review in front of the Firebaugh Building on Friday Avenue in the exhibitor area. There will be daily demonstrations of how the technology works.